Life in Plastic, It’s not Fantastic

Samuel Daughenbaugh, DePauw University

2DA71FE7-975A-4AA8-8A78-DF3D1E545F05The Problem: We live in a plastic world. Plastics have saturated all aspects of our daily lives and, as a consequence, have also entered the natural world.  About 8.3 billion metric tons have been produced in the past 60 years, playing a pivotal role in the advancement of modern society (Parker, 2018). Although they are used to create many things we enjoy and benefit from, there are serious consequences for the health of humans and the environment that are associated with their use.

We have found plastics in unexpected places, everywhere from human guts to the most remote locations on earth (Schwabl, 2018; Woodall, 2014). Plastics have a long list of negative effects on living organisms, but their impact in the ocean is of special concern. Pictures of turtles with straws up their noses, bottle caps spilling out of dead bird stomachs, and penguins strangled in plastic beverage rings are often posted on social media sites. Less widely known are the chemical additives that leach from plastics. Phthalates are one such group of additives that pose threats to the health of humans and marine life.

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Current Fort Johnson REU Interns (Julianna Duran not pictured) collecting plastic and sand dollars on Otter Island. (Photo credit: R. Podolsky)

Phthalates have been valuable to the plastic industry because they promote flexibility and durability in many plastics (EPA, 2017). An astounding 470 million pounds of phthalates are used in the United States every year (EPA, 2017). This presents a significant problem because phthalates interfere with the production of important hormones that regulate growth and metabolism in humans and other animals (Boas et al., 2012).

This summer I am exploring the effects of three different phthalates– dimethyl phthalate (DMP), di-n-butyl phthalate (DBP), and di-2-ethylhexyl phthalate (DEHP)–on the larval development of marine invertebrates, using the purple-spined sea urchin (Arbacia punctulata) as a model. Sea urchin larvae float freely in the water column for an extended period of time and, therefore, are vulnerable to many marine pollutants.

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Purple-spined sea urchin (Arbacia punctulata)

Sea urchins are an important model because they are closely related to humans. Both humans and sea urchins use a signaling hormone called thyroxine, which is especially important for growth in early developmental stages (Heyland et al., 2006). Exposure to phthalates can disrupt the production of thyroxine. Additionally, larvae are very important to study because they form the base of food webs. Being at the bottom of the food chain means they feed animals at higher levels, many of which humans rely on for protein. Therefore, understanding how phthalates affect sea urchin growth and metabolism can lead to new insights into how these pollutants directly and indirectly impact human health.

 Acknowledgements

I would like to thank my mentor, Dr. Robert Podolsky, for his continued support, guidance, and encouragement. This project is supported by the Fort Johnson REU Program, NSF DBI-1757899.

References

Boas, M., Feldt-Rasmussen, U., & Main, K. M. (2012). Thyroid effects of endocrine disrupting chemicals. Molecular and Cellular Endocrinology, 355(2), 240-248. 

Environmental Protection Agency (Ed.). (2017). Phthalates. America’s Children and the Environment, 3, 1-19.

Heyland, A., Price, D. A., Bodnarova-Buganova, M., & Moroz, L. L. (2006). Thyroid hormone metabolism and peroxidase function in two non-chordate animals. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 306B(6), 551-566.

Parker, L. (2018, December 18). A whopping 91% of plastic isn’t recycled. Retrieved from  http://www.nationalgeographic.com

Schwabl, P. (2018, October). Assessment of Microplastic Concentrations in Human Stool. Conference on Nano and microplastics in technical and freshwater systems, Monte    Verità, Ascona, Switzerland.

Woodall, L. C., Sanchez-Vidal, A., Canals, M., Paterson, G. L., Coppock, R., Sleight, V., . . . Thompson, R. C. (2014). The deep sea is a major sink for microplastic debris. Royal      Society Open Science, 1(4), 140317-140317. doi:10.1098/rsos.140317

America’s Continuing Toxic Legacy: Quantifying the Impact of PCBs

Carolina Rios, New York University

The Problem: Polychlorinated biphenyls (PCBs) are a legacy contaminant that pose a threat to human health. PCBs are classified as possible carcinogens and are known to affect neurological development and contribute to diabetes (Xue et. al 2014). Additionally, PCBs are known to alter liver function, impact immune and thyroid function and effect reproduction, as well as gastrointestinal and respiratory health (Hansen 1987). Humans are largely exposed to PCBs by consuming contaminated animal products, such as contaminated fish or dairy (Xue et. al 2014). Similarly, dolphins sampled near Brunswick, Georgia were found to have elevated levels of PCBs, likely due to the consumption of contaminated fish (Wirth et. al 2014). The hydrophobic properties of PCBs mean that they bioaccumulate and can be found in aquatic organisms in concentrations thousands of times greater than the surrounding environment (Nimmo et. al 1974). PCBs also biomagnify up trophic levels in the web, and can be found in even greater concentrations in predator species, as they consume contaminated prey. Thus, the effects of PCBs can be felt throughout the ecosystem.

As PCBs are still relevant contaminants, it is important that we are able to quantify injury associated with PCB levels found in the coastal environment. It is particularly difficult to assess this risk to benthic marine invertebrates (organisms that live in the interface between the bottom of the ocean and the sediment). Therefore, a model has been proposed that predict rates of injury to benthic marine invertebrates (Finkelstein. et al 2017). This model was created through an extensive literature search. However, the data collected as the basis of this mathematical model dates back to the 1970s. In order to verify this model, it is important that we generate new data to verify the accuracy of the model in predicting benthic marine invertebrate injury.

Biphenyl structure. PCBs consist of a biphenyl structure of varying degrees of chlorination. Created using Chemdraw

PCBs were produced for industrial use, such as dielectric fluids, hydraulic fluids, and heat transfer fluids. From 1929 to 1977, PCBs were produced by the Monsanto Corporation in the US, before being removed from production due to negative effects on human health and the environment. Of the 1.4 billion pounds of PCBs produced in the US, it is estimated that one third has entered the environment (Safe et. al 1987). Though they are no longer being produced, their stability and long half-life means that PCBs are still present and continue to pose a real threat to the environment.

Acknowledgements

I would like to thank Dr. Ed Wirth and Brian Shaddrix for their continued guidance and support, as well as my co-mentor Dr. Paul Pennington. Supported by the Fort Johnson REU Program, NSF DBI-1757899.

References

Finkelstein, K. & Beckvar, N. & Dillon, T. (2016). Benthic injury dose-response models for PCB-contaminated sediment using equilibrium partitioning. Environmental toxicology and chemistry, 36 (5), pp. 1311-1329. doi:10.1002/etc.3662.

Hansen, L. (1987). Polychlorinated Biphenyls: Environmental Occurrence and Analysis. In S. Safe (Ed.), Polychlorinated Biphenyls (PCBs): Mammalian and Environmental Toxicology, pp. 15-48. Berlin, Heidelberg: Springer Berlin Heidelberg.

Nimmo, D. & Forester, J. & Heitmuller, P & Cook, G. (1974). Accumulation of Aroclor 1254 in grass shrimp (Palaemonetes pugio) in laboratory and field exposures. Bulletin of environmental contamination and toxicology. 11 (4) pp. 303-308. 10.1007/bf01684932.

Safe S., & Safe, L., & Mullin, M. (1987). Environmental Toxicology of Polychlorinated Biphenyls. In S. Safe (Ed.), Polychlorinated Biphenyls (PCBs): Mammalian and Environmental Toxicology, pp. 1-13. Berlin, Heidelberg: Springer Berlin Heidelberg.

Wirth, E.F., & Pennington, P.L., & Cooksey, C., Schwake, L., & Hyland, J., & Fulton, M.H. (2014) Distribution and sources of PCBs (Aroclor 1268) in the Salepo Island National estuarine research reserve. Environmental Monitoring and Assessment. 186 (12) pp. 8717-8726. doi:10.1007/s10661-014-4039-4

Xue, J., & Liu, S., & Zartarian, V., & Geller, A., & Schultz, B. (2014). Analysis of NHANES measured blood PCBs in the general US population and application of SHEDS model to identify key exposure factors. Journal of Exposure Science and Environmental Epidemiology. 24 (6) pp. 615-621. doi: 10.1038/jes.2013.91